[Show abstract][Hide abstract] ABSTRACT: The three Deleted in Liver Cancer genes (DLC1-3) encode Rho-specific GTPase-activating proteins (RhoGAPs). Their expression is frequently silenced in a variety of cancers. The RhoGAP activity, required for full DLC-dependent tumor suppressor activity, can be inhibited by the Src homology 3 (SH3) domain of a Ras-specific GAP (p120RasGAP). Here, we comprehensively investigated the molecular mechanism underlying crosstalk between two distinct regulators of small GTP-binding proteins using structural and biochemical methods. We demonstrate that only the SH3 domain of p120 specifically and selectively inhibits the RhoGAP activity of all three DLC isoforms as compared to a large set of other representative SH3 or RhoGAP proteins. Structural and mutational analyses provide new insights into the interaction mode of the p120 SH3 domain with the DLC1RhoGAP domain, which is unique and does not follow the classical PxxP-directed interaction. Hence, p120 associates with the DLC1 RhoGAP domain by targeting the catalytic arginine finger and thus by competitively and very potently inhibiting RhoGAP activity. The novel findings of this study shed light on the molecular mechanisms underlying the DLC inhibitory effects of p120 and suggest a functional crosstalk between Ras and Rho proteins at the level of regulatory proteins.
Journal of Biological Chemistry 01/2014; · 4.65 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Induced pluripotent stem cells are generated by direct reprogramming of somatic cells with the introduction of defined transcription factors or other means. Clinical applications of induced pluripotent stem cells are the latest of stem cell therapy approaches due to overcoming problems associated with insufficient cells from conventional sources and immune rejections. In practice, this is restricted by 4 major barriers including the use of genetic manipulations for delivering the reprogramming factors, low efficiency of this process, slow kinetics of the direct reprogramming, and potential for tumor development. Here, we review the latest achievements in improving reprogramming efficiency by alternative strategies. These alternatives mainly involve the replacement of genetic reprogramming factors with small molecules or other factors.
Biochemistry and Cell Biology 12/2011; 90(2):115-23. · 2.92 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Regeneration is a biological phenomenon, which takes place via two main mechanisms: first, dedifferentiation of mature cells followed by their differentiation into functional new cells and second, activation of endogenous somatic stem cells for regeneration of damaged or lost tissues. One of the best examples of healing process in mammals is the regeneration of damaged pinna in rabbits by blastema tissue. The aim of present study was to investigate culture requirements, proliferative properties and expression of some stemness factors in cells derived from regenerating blastema tissue obtained from rabbit pinna in vitro. The regenerating tissues were obtained from male New Zealand white rabbits by double punching of the pinna and cell culture conditions were set to derive and enrich the self renewing cells for further characterisation. The cells were subjected to survival and growth examinations in vitro, and expression of several stemness factors was studied in these cells using reverse transcription polymerase chain reaction (RT-PCR). Results revealed that the derived cells are rather immortal, as they have been growing for more than 120 passages in culture up until this report. Furthermore, RT-PCR and flow cytometry analyses showed that these cells express a number of stemness related genes including Oct4 and Sox2. In conclusion, in this study, stem like cells were derived from blastema tissue of rabbit ears for the first time, showing great self renewing capacity, which provides a suitable in vitro model for regeneration studies. Moreover, they could be considered as a good source of stem like cells for future applications.